Negative-acting photoresist compositions have been used commercially for many years. These compositions are applied as a layer over a substrate and then subjected to actinic radiation. The actinic radiation causes a change in solubility of the layer, usually by photoinitiated polymerization of components within the layer. When the imaged layer is subsequently treated (e.g., washed and lightly scrubbed) with a developer solution, such as an aqueous alkaline solution of pH greater than 12, the non-light struck areas of the layer are washed away. If the original layer contained a colorant material (e.g., dyes or pigment), development would leave an imagewise distribution of the colored layer as a final image. If an etching or plating process is performed on the developed layer, an etched or plated image is deposited on the substrate in the exposed areas where the photoresist layer had been removed by development. A wide variety of photoresist compositions exist in the art, and many have been used as photosensitive printing plate compositions in lithographic technology. Examples of photoresist compositions known in the art include U.S. Pat. Nos. 3,395,016, 3,469,982, 3,639,185 and 4,193,797, as well as Canadian Pat. Nos. 976,352 and 976,353.
Most of the negative-acting photoresist compositions known in the art use ethylenically unsaturated materials in combination with a free radical generating photoinitiator as the active ingredients. Acrylic functional materials (i.e., acrylyol and methacrylyol functional materials) are generally preferred in the art because of their speed, toughness upon cure, and moderate cost. Printing plate compositions, in particular, rely on the use of acrylic functional materials in various forms such as monomers, oligomers and polymers with acrylic functionality. Examples of such printing plate compositions and the use of various acrylic functional materials are shown, for example, in U.S. Pat. Nos. 4,316,949, 4,228,232, 4,104,072 and 3,954,475. Many of these compositions have found acceptable commercial uses, but they have tended to be weak in certain technically important areas, particularly toughness of the cured composition, tackiness of the uncured composition, and cold flow of the resist layer.